1. Field of the Invention
This invention relates to manually propelled wheelchairs and their construction, and more particularly to a wheelchair construction that affords the disabled user not only mobility, but proper seating and positioning, as well.
2. Prior Art
Over the past 60 years the development of the metal manually propelled wheelchair has provided many who would otherwise have been shut out of society because of their disability a way to return to the mainstream. During the most recent decade, in response to the growth in the number of disabled and heightened public awareness of their problems, great strides have been made in the direction of decreasing the weight and improving the efficiency, durability, and maneuverability of both folding and non-folding wheelchairs. Technological progress has not been without its drawbacks, however.
The manufacture of a conventional wheelchair involves the fabrication, sub-assembly, and assembly of as many as two hundred fifty or three hundred individual parts. The production of each unit is complex and time consuming because certain parts and components have to be fabricated specifically for each wheelchair. Wheelchairs today are manufactured in frame widths from 10" to 20", frame depths from 14" to 18", and varying back heights, seat heights, configurations, materials, finishes, and colors. For the manufacturers, the diversity and inherent inefficiencies of the new designs have driven up production and inventory costs and created stocking nightmares. Similarly, for the distributors and retailers, maintaining an adequate inventory to fill all the possible combinations is extremely difficult and expensive.
Another major deficiency in current wheelchair design is that most of the dimensions must be chosen at the time the chair is ordered. Modifying the typical wheelchair after manufacture, for example, to correct a mistake in the order or to meet the changing needs of the user, is difficult and, in some instances, impossible. A few of the prior art designs provide for certain changes. These generally require the costly addition or replacement of wheelchair components, however, or the equally costly adjustment or modification of existing components by a specially trained service technician.
Additionally, for all of its advances, the present wheelchair technology offers little in the way of improved seating. With few exceptions, contemporary wheelchairs still use the sling seats and seat backs and fixed mounting structures that were designed for the wheelchairs of the 1940's. Sling seating has a number of shortcomings: It is uncomfortable and over time is ruinous to good posture. Being flexible, it cannot provide stable support to the user when the wheelchair is in motion, and particularly when he or she is propelling the chair manually. And it is not readily adjustable to position the user either for the most efficient use of the drive wheels, or for the most desirable balance.
Although the limitations and deficiencies inherent in this type of seating are well known, scant attention has been paid by the wheelchair designers to the sitting comfort, posture, stability, and positioning of the disabled user. Most of the advances in these areas have come in the form of various devices, such as solid seats and backrests, cushioned interfaces, fabric covers, and the like, that are made to mount on, or attach to, existing wheelchairs. To adjust user's position or the chair's balance, the common method is to provide means for repositioning the wheels or the casters on the chassis.
As a rule, because these products are "add-ons," rather than integrated components of the initial design, they tend to be cumbersome and awkward to use. Generally, they require substantial hardware and considerable effort to install. Furthermore, since there is little, if any, standardization among the various makes and models of wheelchairs on the market, these retrofit devices are generally designed for use with a specific wheelchair or type of wheelchair construction. As in the case of the wheelchair designs, the diversity and inefficiency of these seating devices makes their manufacture, stocking, inventorying, and modification difficult and expensive and likely to remain so.
Viewed against this background, one object of the subject invention is to provide a wheelchair construction that affords the advantages and overcomes the deficiencies inherent in prior art wheelchairs.
Another object is to provide a wheelchair contruction that is sturdy, lightweight, and durable.
Yet another object is to provide a wheelchair that incorporates proper seating for the disabled user as an integral part of its construction.
An additional object is to provide a wheelchair construction in which the user's center of gravity is shifted longitudinally of the frame by moving the seat on the frame rather than by moving the wheels on the frame.
A more particular object is to provide a wheelchair construction of this type that can be fabricated from a minimum number of parts.
Still another object is to provide a wheelchair construction that incorporates in a single integrated structure a unitary lower main frame supporting the wheels and casters, and an adjustable upper seating assembly.
A further object is to provide a wheelchair construction of this type that permits the standardization and use of interchangeable individual parts and modular components.
A still further object is to provide a wheelchair construction of this type having means for adjusting the wheelbase, frame-pitch, wheel and caster tracking, drive wheel and caster camber, seat length and height, seat back height, seat and seat back longitudinal positioning, armrest width and height, footrest length and depth, and push-handle configuration and positioning.
Yet a further object is to provide a wheelchair construction satisfying all of the foregoing objects that is comparatively inexpensive to manufacture and requires a minimum of maintenance and repair.
Other objects will become apparent from the following summary of the invention and detailed description of its preferred embodiments.